Groovy for Domain-specific Languages - Second Edition

Chapter 7

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static String sentMessage

static def sendMessage1(id, message) {

sentMessage = "Sending (${message}) to ${id}"

}

given:

sendMessage1 "GroovyDSL", "Hi from GeeTwitter"

expect: "message sent correctly"

sentMessage == "Sending (Hi from GeeTwitter) to GroovyDSL"

when:

sendMessage1 "Hi from GeeTwitter", "GroovyDSL"

then: "message sent incorrectly"

! (sentMessage == "Sending (Hi from GeeTwitter) to GroovyDSL")

The second invocation here would, of course, cause an exception in the real
GeeTwitter as we try to send a message to a user called "Hi from GeeTwitter"
instead of to GroovyDSL. A small change removes this ambiguity and improves the
readability of the DSL:

static def sendMessage2(Map params, message) {

sentMessage = "Sending (${message}) to ${params.to}"

}

when:

sendMessage2 to: "GroovyDSL", "Hi from GeeTwitter"

then: "message sent correctly"

sentMessage == "Sending (Hi from GeeTwitter) to GroovyDSL"

when:

sendMessage2 "Hi from GeeTwitter", to: "GroovyDSL"

then: "message sent incorrectly"

sentMessage == "Sending (Hi from GeeTwitter) to GroovyDSL"

It might seem a little redundant or inefficient, from a programming point of view, to
package a single value in a map. However, even though we are only going to pass
the single value to a parameter along with a message parameter, naming this to
parameter adds significantly to the resulting DSL script in terms of legibility.